1. Field of the Invention
This invention relates generally to carton sealing apparatus, and is particularly concerned with apparatus for sealing an end closure of a thermoplastic coated paperboard carton by ultrasonic vibration.
2. Description of the Prior Art
The prior art includes various apparatus for sealing containers of thermoplastic material both by the direct application of heat, and by the generation of heat by ultrasonic vibration. Examples of prior art apparatus of this type are disclosed in U.S. Pat. Nos. 3,200,557; 3,307,325; 3,309,841; 3,468,731; 3,531,908; 3,562,041; 3,579,958; 3,681,167 and 3,717,539, as well as German Auslegeschrift 2,165,620.